Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) remove material from the surface of workpieces. These workpieces can include wafers or other microelectronic substrates in the production of microelectronic devices and other products. One goal of CMP processing is to consistently and accurately produce a uniformly planar surface on the workpiece to enable precise fabrication of circuits and photo-patterns. During the construction of transistors, contacts, interconnects and other microelectronic features, many workpieces develop large “step heights” that create highly topographic surfaces. Such highly topographical surfaces can impair the accuracy of subsequent photolithographic procedures and other processes that are necessary for forming sub-micron features. For example, it is difficult to accurately focus photo patterns within tight tolerances on topographic surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical surface into a highly uniform, planar surface at various stages of manufacturing microelectronic devices on a substrate.
To create a planar surface on a workpiece, a CMP system typically includes a workpiece carrier that presses the workpiece against a rotating planarizing pad. A slurry, such as an abrasive slurry, is also typically used to facilitate the planarization and material removal from the surface of the workpiece. During the planarizing process, however, many different factors can affect the planarization or material removal rate. Such factors include, for example, variances in the distribution and size of abrasive particles in the slurry, topographical areas with different densities of features across the workpiece, the velocity of the relative movement between the workpiece and the planarizing pad, the pressure with which the workpiece is pressed against the planarizing pad, the condition of the planarizing pad, etc.